Abstract
SUMMARY: A survey of the variation in the pathogenicity of 22 populations of the cereal root eelworm was carried out using three barley and two oat genotypes. Of the barley genotypes tested, the cultivar Cb 545 (Rika) was susceptible to all populations, while the unadapted six‐row genotype Cb 824 (No. 191) was resistant to all populations except one, a population from Akenham in Suffolk, to which it was partially susceptible. The two‐row cultivar Cb 917 (Fero) showed a range of reactions to the 22 populations from complete resistance to complete susceptibility. Of the oat genotypes used, S 225 (Milford) was susceptible to all populations, while Cc 4658 (I 376, Avena sterilis) was resistant.The results presented indicate that there are at least three pathotypes of the cereal root eelworm in England and Wales.